Abstract
The vacuolar membrane ATPase of Neurospora crassa closely resembles the mitochondrial ATPase in its substrate specificity, substrate affinity, and sensitivity to the inhibitor N,N'-dicyclohexylcarbodiimide. Three different mutants with altered mitochondrial ATPase activity, exhibited as 1) resistance to N,N'-dicyclohexylcarbodiimide, 2) enhanced sensitivity to N,N'-dicyclohexylcarbodiimide, and 3) very low specific activity, were found to be unaltered in the vacuolar membrane ATPase. The vacuolar membrane ATPase was similar to the mitochondrial ATPase and approximately 10-fold more sensitive than the plasma membrane ATPase in its sensitivity to the inhibitors 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, 2',3'-O-(2,4,6-trinitrophenyl) adenosine 5'-triphosphate, and 5'-adenylylimidodiphosphate. By contrast, the vacuolar ATPase resembled the plasma membrane ATPase in its response to quercetin (both 10-fold more sensitive than the mitochondrial ATPase); it was unique in its sensitivity to KNO3. A N,N'-dicyclohexylcarbodiimide-binding protein, migrating between molecular weight markers of 14,400 and 21,500, was identified as a putative component of the vacuolar membrane ATPase. Taken together, these findings support the argument that the vacuolar membrane ATPase is a distinct enzyme, more like the mitochondrial F0F1 ATPase than the plasma membrane ATPase.
Highlights
N,N’-dicyclohexylcarbodiimide,and 3)very low spe- basic characteristics with ATPasesdescribed in several other cific activity, were found to be unaltered in the vacuolar membrane ATPase
The vacuolar membrane ATPasewas similar to the mitochondrial ATPase and approximately 10-fold more sensitive than the plasma membrane ATPase in its sensitivity to the inhibitors 7-chloro-4-nitrobenzo-2-oxa-l,3-diazole2,’,3’-0(2,4,6-trinitrophenyl) adenosine 5‘-triphosphate, and organelles, including yeast vacuoles [9], plant vacuoles [10, 11], animallysosomes [12], and animalsecretory vesicles (1315)
Olar ATPase resembled the plasma membrane ATPase,more recent evidence has suggested that a novel in its response to quercetin; it was unique in its ule membranes and that the mitochondrial-type ATPase resensitivity to KN03
Summary
N ,N’-dicyclohexylcarbodiimide,and 3)very low spe- basic characteristics with ATPasesdescribed in several other cific activity, were found to be unaltered in the vacuolar membrane ATPase. Reacstrains of Sebald andco-workers (reviewed in Ref. 28) contain a mitochondrial ATPase that is resistant to oligomycin and is 5 - to 10-fold more sensitive to DCCD than the wild type ATPase.Similarresults were obtained using the oli 16-16 tion mixture contents for mitochondrial and plasma membrane AT- strain of Edwards and Unger [21] subsequently crossed into
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